Firstly, Google Maps Wants Your Search History: Google's "Web & App Activity" settings describe how the company collects data, such as user location, to create a faster and "more personalised" experience.
This means that every single place you've looked up in the app -- whether it's a strip club, sex shop, brothel, fish and chip shop or your dealer's location -- is saved and integrated into Google's search engine algorithm for a period of 18 months. Google uses "dark patterns" user interfaces crafted to coax us into choosing options we might not otherwise, for example by highlighting an option with certain fonts or brighter colours.
Google Maps limits its features if you don’t share history. When opening the Google Maps app, you will see a circle in the top right corner that signifies you're logged in with your Google account. That is not necessary, and you can simply log out. The log out button is slightly hidden but can be found like this: click on the circle > Settings > scroll down > Log out of Google Maps. Unfortunately, Google Maps will not let you save frequently visited places if you are not logged into your Google account. If you choose not to log in, when you click on the search bar you get a "Tired of typing?" button, suggesting you sign in, and coaxing you towards more data collection.
Google Maps can tell the cops all about you. The "Google Maps Timeline," shows an estimate of places you may have been and routes you may have taken based on your Location History. With this feature, you can look at your personal travel routes on Google Maps, including the means of transport you used, such as a car or a bike.
This means that information is available to anyone with access to your account. Google may also share data with government agencies such as the police. If your "Location History" is on, your phone "saves where you go with your devices, even when you aren't using a specific Google service". This feature is useful if you lose your phone, but also turns it into a tracking device.
Google Maps often asks users to share a quick public rating. "How was Berlin Burger? Help others know what to expect", suggests the app after you've picked up your dinner. All this info is collected in your Google profile, making it easier for someone to figure out if you are visiting a place briefly and occasionally - like on holiday - or if you live nearby.
Google gets away with all this by making it appear that it is good for you. It tells you it uses this data for all kinds of useful things, like "security" and "language settings" -- and, of course, selling ads. Google sells advertisers the possibility to evaluate how well their campaigns reached their target and how often people visited their physical shops "in an anonymised and aggregated manner". But only if you opt in or forget to opt out.